Manufacture of a multicolor lead



y 9 1939. a R. Z L JcKERT 2,165,827

MANUFACTURE OF A MULTICOLOR LEAD Filed April 15, 1936 WV v,

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Patented July 11, 1939 UNITED STATES MANUFACTURE OF A MULTIC'OLOR LEADRichard Ziickert, near Budweis, Czechoslovakia, assignor to firmKoh-i-noor Tuzkarna L. & C. Hardtmuth, Ces. :Budejovice, CzechoslovakiaApplication April 15, 1936, Serial No. 74,470 In Germany April 2'7, 1935LGIaim. (Cl. 18-61) The invention relates to the manufacture of a leadfor pencils by means whereof it is possible to write in a plurality ofcolors, so that the written stroke or mark as a rule exhibits at leasttwo 5 colors adjacent one another, and said colors change rapidly.

Processes are already known for the manufacture of two-colored ormulti-colored leads, either by simultaneous extrusion from a nozzlehaving a plurality of color channels uniting in the said nozzle, or bygluing together a plurality of singlecolored leads, or by assemblingpieces of the color compositions, which in cross-section have the shapeof circular segments, so as to form a cylinder. This cylinder of colorcomposition is then handled in the ordinary lead pencil extrusion presshaving ordinary cylindrical containers for extruding the composition.

The fundamental disadvantages of these known processes is that whenusing the leads manufactured by them, the color changes much tooinfrequently, so that it is necessary to write much too long with thesame color. The reason for this is that in all the processes, thepossible number of color components in the lead is too small. In thelast-mentioned known process, however, even with a large number of colorcomponents (in the factory it will scarcely be possible to join togetherproperly more than six segments to form a cylinder), the boundary facesbetween two colors in the cylinder of color composition, and later inthe lead, lie relatively close together only at the centre of the shaft,while they diverge rapidly towards the periphery. A pointed lead isused,

the writing point moves outwardly more and more from the centre of theshaft towards the periphery of the shaft, and the change in color willbe more infrequent, so that the pencil marking is of the same color fora longer period.

A further disadvantage of the last-mentioned segment process resides inthe fact that the separation of a cylindrical core into segments and there-assembling of differently colored segments to form a new shaft orcore, cannot be eifected (on account of the blade-like shape of thesegments in the case of a large number of components) so accurately asto leave no air between the individual segments. In extruding thecomposition from an extrusion nozzle, this air prevents an intimateunion between the individual segments. A lead produced in this wayexhibits radially extending fissures which considerably impair itsstrength.

All these disadvantages are obviated with the 5 present invention.According to the invention,

rality of a composition body, likewise composed of a pluaxially-directedcomponents, each single-colored in itself, is extruded through a singleorifice, but the individual single-colored components of the compositionbody have a square, rectangular or other cross-section without acuteangles, which makes it possible to semble and press the single-colorcomponents together during the extrusion process without any gaps, andto form a composition body which in 10 cross-section has a checkeredpattern in different colors.

A simple and therefore advantageous form of carrying out this processcomprises extruding by the normal manufacturing process used for 15making the shaft of a lead pencil, a quadrangular rod having a squarecross-section and assembling a number of these rods into a compositebody or block having a cross-section which is sub-divided into manycolors in a checkered pattern, then in- 20 troducing this composite bodyinto a composition container of square cross-section, and extruding saidcomposite body from the container through a preferably cylindricalextrusion nozzle, in order to form a cylindrical lead or shaft. 25

The process according to the invention has first of all, the advantagethat by means thereof, it is possible to combine any desired largenumber of components in the composite body, since the (lo-centralisationin the cross-sectional distribu- 30 tion of the components renders theprocess independent of the number of such components. There is,furthermore, the further advantage that the individual components arevery easy to manufacture, due to the fact that their cross-section 35 isof simple shape, and their air-free assembly may also be carried outwithout any difficulty for the same reason. It is also possible toremove the air from the assembled composition body by tapping andpressing it (as by tapping 40 its outer surface), so as to free it fromthe last residue of air which may still be present, without the fear ofthereby weakening the cohesion of the components.

Fig. l is an end view of a composite slug or 45 cartridge which may beformed and extruded, according to the invention.

Fig. 2 is a cross-section of a cylindrical pencil shaft which has beenmade by extruding the body illustrated in Fig. 1. Fig. 2 is drawn to 50enlarged scale.

To provide a numerical example, it is, for example, easily possible,according to the invention, to use a composition container of squarecross-section, the length of a side of this cross" section being 80 mm.This container can be used with an extrusion nozzle, to press and tocombine into a block, 64 lead rods, of four different colors for exampleeach rod having a square cross-section, the length of a side of suchcross section being 10 mm. This is shown in Fig. 1. If this block isformed by extrusion into a cylindrical lead of 2.6 mm. diameter, thelength of side of the squares of the checker pattern will be reduced toabout 0.3 mm. Since the width of a Written line is about 0.3 to 0.6 mm.,the probability of the stroke being in two colors is very great evenwith this dimension. With these dimensions, 49 points of intersection ofcolor boundaries are distributed over the interior of the cross-sectionof the lead, while the lead, if subdivided in segment form only containsone such point of intersection. The length of side of the colorcomposition components of square crosssection may be reduced stillfurther without any difficulty, and the number of rods of differentcolors in one lead or shaft may be increased, thereby providing withcertainty the probability that each stroke will consist of at least twocolors.

The four different colors in Fig. 1 are indicated by different kinds ofshading.

As shown in Fig. 2, the completed shaft has a checkered pattern incross-section, although the straight boundary lines in the originalcomposite body have been distorted.

For the purpose of defining the invention in the claim, it is noted thatI extrude a slug or cartridge having elements of different colors sothat the transverse cross-section of said slug or cartridge has acheckered pattern in which the elements of said composite slug orcartridge are free from acute angles. Likewise the elements of saidcomposite slug or cartridge have longitudinal surfaces whichsubstantially abut each other so that air spaces are eliminated whensaid composite slug or cartridge is extruded to make the shaft.

I claim:

The method of forming a cylindrical multicolored pencil shaft whichcomprises assembling a plurality of shaft elements of plastic materialand of different colors with their faces in contact with each other,each of said shaft elements being in the form of a rod of substantiallysquare cross-section, said elements being assembled into the form of ablock having square cross-section, and extruding said block through acircular oriflee in a direction longitudinally of said block.

RICHARD ZTL ICKERT.

